This invention pertains to a modular, cushioning orthodontic bracket structure mountable on a conventional orthodontic tooth band. More particularly, it concerns such a structure which includes outer and inner releasably interengageable bracket members that are formed of materials having different degrees of elastic stiffness.
As is well understood, orthodontics involves the application of forces to teeth to change their positions and/or orientations in the mouth. Typically, a bracket is fastened to a tooth, with a band or by direct bonding to the enamel of the tooth. The bracket is for the purpose of receiving a force-inducing arch wire. A widely used orthodontic technique, in the setting of such apparatus, involves the preshaping or bending of an arch wire at the location of selected tooth brackets so that appropriate forces are applied to the associated teeth when the wire is tied, or ligated, to the particular brackets. Another technique which has been proposed involves the use of an insert in a tooth bracket, which insert is formed with an angled or rotated slot that receives an arch wire. In this kind of a setting, pre-bending of an arch wire at the location of such an insert is not necessary. Rather, insertion of the arch wire in such a slot deforms the arch wire which, as it tries to restore its position, applies a tooth-positioning force.
These prior techniques, however, do not adequately deal with the problem of shock that occurs to teeth newly exposed to a tooth-positioning force. More specifically, these prior art techniques involve extremely rigid structures which can, and most often do, result in a significant amount of discomfort shortly after the affixing of an arch wire. Further, the rigid and tight connections which have existed heretofore between conventional arch wires and bracket structures usually produce a relatively high-friction condition which tends to impede, in some instances, movement of a tooth. This results from binding between an arch wire and bracket.
A general object of the present invention is to provide a novel modular, cushioning orthodontic bracket structure which offers all of the advantages of the above-discussed prior art techniques, while significantly minimizing the disadvantages.
More specifically, an object of the invention is to provide such a bracket structure which minimizes tooth shock and discomfort, and which maximizes low-friction movability of a tooth along an arch wire.
According to a preferred embodiment of the invention the proposed bracket structure includes outer and inner releasably interengageable bracket members. The outer bracket member has the form, generally, of a conventional so-called standard-twin edgewise bracket of the type first discussed above, with this member being formed from a material having a relatively high degree of elastic stiffness. This outer member, when used, is secured as by welding to a conventional tooth band, or to a direct bonding pad and includes a special socket for snap-receiving the inner member in the structure. In particular, this socket is intended to capture a received inner member in what is referred to herein as an omnidirectionally fixed-captured manner. In other words, while removal of a received inner member is possible, when the member is in place it is substantially firmly held against any significant movement in any direction relative to the outer member.
The inner member, conversely, is formed of a material having an appreciably lower degree of elastic stiffness. This member includes a slot for receiving a conventional arch wire. The slots, in certain particular inner members, are shaped to define the specific positional orientation of an arch wire received therein, so as to effect, through deforming the arch wire, the transmission of predetermined forces from the wire to an outer bracket member, and thence to an associated tooth.
With such a construction, pre-bending of an arch wire, according to the prior-art technique first-described above, is not necessary. Further, a tooth-positioning force is transmitted in such a manner as to minimize shock. For example, with initial installation of an arch wire, resiliency in the lower-stiffness inner member deforms to store a significant amount of potential energy due to the force exerted by the arch wire as it tends to restore its undeformed condition. This action greatly reduces the discomfort-producing effects of arch wire installation. This more pliant inner member, through such energy storage, promotes the continual and gradual application of a corrective force.
Also, materials which have been found to function well for forming the inner member in the proposed structure have also been found to offer relatively low-friction contact with an arch wire. This, of course, minimizes the binding problem mentioned above, and facilitates tooth movement along an arch wire.
These and other objects and advantages which are obtained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.